Many space operations of the future will require the use of long lightweight deployable booms. These booms have application in a number of areas such as a mast to support and accurately position the feed-horn for large antennas, to deploy and provide tension in the blankets of a solar array, or to serve as structural components of a space station or operations center. A number of deployable and/or extendable structural configurations have been proposed in the past, most of which are truss-type structures composed of load carrying axial members (longerons) stabilized by cross-members (battens) and diagonals. The prior art truss configurations have either telescoping or folding longerons connected directly by diagonals, which are generally constructed of cable to facilitate folding and/or packaging. The cable must be pretensioned or the structure will have low shear stiffness until the deformation is adequate to load the diagonal members. However, pretension in the diagonals introduces load in the longerons making them less efficient structural members. Column or compression loads applied to the longerons will also reduce the tension in the wire diagonals.
Some of these problems can be overcome by using diagonals fabricated from members that have bending stiffness adequate to support compression loads. However, trusses with single diagonals may introduce bending or kick loads in the longerons when the truss is loaded in compression. Trusses with cross-diagonals, while eliminating this problem, are more difficult to fold and the diagonals must be adequate to support not only loads introduced by shear, but structural redundancy causes part of the axial load to be introduced in the diagonals. Trusses with folding members also require the lengths of all members to be precisely set and the stiffness of the deployed structure is significantly affected by tolerance in the joints.